CVE-2018-5711 Explained : Impact and Mitigation

An integer signedness error in gd_gif_in.c, part of the GD Graphics Library (libgd) used in PHP versions before 5.6.33, 7.0.x before 7.0.27, 7.1.x before 7.1.13, and 7.2.x before 7.2.1 can lead to an infinite loop when processing a specially crafted GIF file.

Understanding CVE-2018-5711

This CVE involves a vulnerability in the GD Graphics Library used in various PHP versions, potentially causing an infinite loop when handling specific GIF files.

What is CVE-2018-5711?

This CVE identifies an integer signedness error in gd_gif_in.c, a component of the GD Graphics Library (libgd), which is utilized in PHP versions prior to 5.6.33, 7.0.x before 7.0.27, 7.1.x before 7.1.13, and 7.2.x before 7.2.1. The flaw can trigger an infinite loop during the processing of a maliciously crafted GIF file, specifically when invoking certain PHP functions.

The Impact of CVE-2018-5711

The vulnerability can be exploited to cause an infinite loop, potentially leading to denial of service (DoS) conditions or other adverse effects on systems running the affected PHP versions.

Technical Details of CVE-2018-5711

This section delves into the technical aspects of the CVE.

Vulnerability Description

The flaw in gd_gif_in.c within the GD Graphics Library allows for an integer signedness error, resulting in an infinite loop when handling a manipulated GIF file through specific PHP functions.

Affected Systems and Versions

PHP versions before 5.6.33
PHP 7.0.x before 7.0.27
PHP 7.1.x before 7.1.13
PHP 7.2.x before 7.2.1

Exploitation Mechanism

The vulnerability can be exploited by utilizing the imagecreatefromgif or imagecreatefromstring functions in PHP to process a specially crafted GIF file, triggering the infinite loop due to the integer signedness error.

Mitigation and Prevention

Protecting systems from CVE-2018-5711 involves implementing appropriate mitigation strategies and security measures.

Immediate Steps to Take

Update PHP to versions 5.6.33, 7.0.27, 7.1.13, or 7.2.1 or later to address the vulnerability.
Monitor for any unusual system behavior that could indicate exploitation of the flaw.

Long-Term Security Practices

Regularly update PHP and associated libraries to ensure the latest security patches are applied.
Conduct thorough security assessments and testing to identify and remediate vulnerabilities proactively.

Patching and Updates

Stay informed about security advisories and updates from PHP, GD Graphics Library, and relevant vendors to promptly apply patches and protect systems from known vulnerabilities.